You don't "need" it defaults to the shareware version if you don't provide the MPQ. I will say though that the original Diablo discs are archived on archive.org...

This will still get shut down

Remember REVC?

Nope, been playing it for a couple days now. It's just the same as it ever was. The web port itself is seamless (been playing on Firefox with a 10-year-old Macbook), but the game has a clunky, PITA UI.

It's kinda maddening in that no matter how well you clear every level, your character is likely to stall at some point and you'll have to start over. For anybody who doesn't know, you can start the game over again using the same character and re-loot the same levels; they don't respawn once you clear them otherwise. In this way you can continually train up your character to make it further into the dungeon. At first it seems like this was a mistake, but then it seems that it actually was a design decision. It was the first of its kind, so it gets a pass I suppose.

The shopkeepers inventory also does not cycle until you buy something and then that slot refills. So whatever you've got is what you've got. Unlike most of the games that came after, you are actually somewhat dependent on the shopkeepers for decent gear.

That said, it's still fun. Really fun. It's not hard to see why it started something.